As many as 5 million Americans may have Alzheimer’s disease, according the National Institutes of Health, and more than half of all Americans are close to someone who has it. At the center of HBO’s ambitious new project­ are four documentaries, starting with TheMemory Loss Tapes (May 10, 9 p.m.), which follows seven people afflicted with Alzheimer’s. The two-part Momentum in Science (May 11–12, 8 p.m.) explores the latest research on the disease; “Grandpa, Do You Know Who I Am?” With Maria Shriver (May 11, 7:30 p.m.) shows its effect on children and grandchildren; and Caregivers (May 12, 7 p.m.) spotlights the sacrifices of family members. The project also includes 15 short films, a website (HBO.com/alzheimers), and a community campaign. Sunday–Tuesday, May 10–12, HBO